Snap acting switch mechanism



May w, WWI c. GAMBILL ETAL 3,a2@,384

SNAP ACTING SWITCH MECHANISM 2 Sheets-Sheet 1 Filed June 27, 1963INVENTORS (HA/WEE 6. 6A MB lF/ffi/ARD 5. GAUGLER BY ATTORNEY May 16,1967 (3. c. GAMBILL ETAL 3,

SNAP ACTING SWITCH MECHANISM Filed June 27, 1963 2 Sheets-SheetINVENTORS CHARL E5 C. GA MB/L L R/CHARD 5. GA UGL ER BY ATTORNEY UnitedStates Patent Ofifice 3,320,384 Patented May 16, 1967 3,320,384 SNAPACTING SWITCH MECHANISM Charles C. Gambill, Tipp City, and Richard S.Gaugler,

Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Filed June 27, 1963, Ser. No. 291,117 3 Claims.(Cl. 200-122) This invention relates to control systems for electricaldevices and more particularly to an improved controller for theelectrical surface heater of a kitchen range or the like.

Many electrical control systems have circuit breaking contacts connectedacross relatively high voltage sources in the range of 115 to 230 voltswhich tend to weld together during the controlling operation. It istherefore desirable to provide contact actuating means which separatethe contacts by a snap action as they are moved into their open positionupon the occurrence of a predetermined event or condition. In manyapplications it is desirable that such contact actuating means have aselectively variable effect on the circuit breaking contacts in order toproduce a modulated control of an electrical device associatedtherewith.

An object of the present invention, therefore, is to improve electricalcontrol systems having circuit breaking contacts by including improvedmeans therein for positively separating the circuit breaking contactsand moving them into an open position.

Another object is to improve electrical controllers having a pair ofcircuit controlling contacts by the provision of a thermally responsiveelement having a predetermined transition temperature at which theelement initially expands a predetermined amount to open the controllingcontacts for carrying out a given control function.

A further object of the invention is to improve an electrical controlleractuated by such a thermally responsive element by the provision ofmeans for regulating the rate of temperature increase of the thermallyresponsive element for modulating the controlling action thereof.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

' In the drawings: 7 FIGURE 1 is a view in perspective of a portion ofan electrical range including the present invention;

FIGURE 2 is a schematic view of the controller of the present invention;

FIGURE 3 is a view in front elevation of a structural embodiment of theimproved controller with the front cover and control knob thereofremoved;

FIGURE 4 is a view in horizontal section taken along the line 44 ofFIGURE 3 with the front cover and control knob shown;

FIGURE 5 is a view in vertical section taken along the line 55 of FIGURE3;

FIGURE 6 is a view in horizontal section taken along the line 66 ofFIGURE 3;

FIGURE 7 is a view in vertical section taken along the line 7-7 ofFIGURE 3;

FIGURE 8 is a view in vertical section taken along the line 8-8 ofFIGURE 3; and

FIGURE 9 is a schematic view of another embodiment of the invention.

Referring now to FIGURE 1, an electrical range 10 is illustrated ashaving an electrical resistance coil or surface heater unit 12representing a typical electrical device regulated by a controller 14constructed in accordance with certain of the principles of theinvention. In FIGURE 2 the controller 14 is shown associated in anelectrical system including a suitable source of power 16 such as aresidential electrical system of volt power connected to lines 18, 20.Line 18 is electrically connected to a fixed contact 21 adapted toengage a movable contact 22 supported by and electrically connected toone end of a cantilevered spring arm 24 of conductive material biasedinto engagement with the outer periphery 25 of a rotatable cam 26 havinga notched portion 28 therein for receiving an offset portion 30 of thearm 24 when the contacts 21, 22 are in an open position as shown. Thespring arm 24 is rigidly secured at its other end to a suitable fixedsupport 31. The contacts 21, 22 serve as an on-off switch for theimproved controller as will be discussed.

The cam 26 is supported on a shaft 32 connected to a manually rotatabletemperature control knob 34 having a suitable scale 36 thereon movablerelative to an indicator 37 for selecting a predetermined operatingtemperature or other desired condition of operation for the electricalheater or range surface heating element 12.

When the control knob 34 is moved from its off position, the cam 26 willbias the arm 24 to close the contacts 21, 22 to thereby complete acircuit through a conductor 38 electrically connected between the arm 24and the heater 12 and thence through a conductor 39 electricallyconnected between the heater 12 and a thermally responsive conductiveelement 40, a conductor 42, a cantilevered spring arm 44 of conductivematerial having one end thereof supporting a movable contact 46 which isbiased thereby against a fixed contact 48 electrically connected to theline 20. The opposite end of arm 44 is anchored on a suitable fixedsupport 49.

The thermally responsive conductive element 40 has one end thereofrigidly secured to a suitable fixed support 50 and the opposite endthereof in contact with the spring arm 44. Intermediate the ends of theelement 40 is a channel-shaped member 52 spring biased by means of aspring element 54 against a curve-d surface 56 on the cam 26. Thechannel-shaped element 52 is movable by the cam surface 56 relative tothe conductive element 40 so that a greater or lesser portion of arms58, 59 on either side thereof are located in overlapping relationshipwith the element 40.

In accordance with certain of the principles of the pres ent invention,the conductive element 40 is a thermally responsive material having apredetermined transition temperature at which it will expand apredetermined amount to operate the contacts 46, 48 to thereby terminateenergization of the heater 12. One example of a material having suchexpansion characteristics is Mn Cr Sb. This material has little or nolinear expansion below a predetermined transition temperature which isdependent on the quantity (x) in the above-described formula but whenthe temperature of the element 40 reaches a predetermined transitiontemperature, it will suddenly expand a-predetermined amount sufficientto deflect the spring arm 44 upwardly to cause a snap action opening ofcontacts 46, 48. In the above-described improved control arrangement theelement 40 is in cluded as a conductor portion of the electrical heatercircuit and accordingly when the contacts 21, 22 and contacts 46, 48 areclosed current flow through the element 40 will cause it to self-heat tothereby increase the temperature thereof to the predetermined transitiontemperature at which it will expand to produce the abovedescribedcontact opening action.

In order to modulate the heat ouput of the surface heater 12 the controlknob 34 is rotated to a predetermined temperature setting to cause thecam 26 to shift the channelshaped element 52 into a greater or lesseroverlapping relationship with the element 40. The channel-shaped element52 is made from a material having good thermal conductive properties andhence serves as a variable heat sink to thereby produce a greater orlesser heat transfer from the element 40 during the periods in which itis heated. For example, when the element 52 is in its greatestoverlapping relationship with the element 40, a

relatively great amount of heat is conducted thereby from the element 40to delay the time required to reach the above discussed predeterminedtransition temperature at which the element will expand. Accordingly,the surface heater '12 remains energized for a relatively long durationbefore the element 40 will reach the transition temperature at which itinitially expands to open contacts 46, 48.

Following opening of the contacts 46, 48, the element 40 cools below thetransition temperature thereof and consequently contracts to again allowthe spring arm 44 to close the contacts 46, 48. The element 40 willcontinue to pulsatingly regulate the length of time that power issupplied to the heater 12 at the above-described duration ofenergization until the control knob 34 is moved into another position,for example, to -a position where the element 52 will barely overlie theelement 40. In this case, there is lesser thermal conduction to element52 from the element 40 and it will, accordingly, reach the transitiontemperature through self-heating at an earlier point in time to open thecontacts 46, 48. The element 40 will again cool and reheat to thetransition temperature at an increased rate to reduce the average powerinput to the surface unit and hence reduce the heat output therefrom ina selected fashion. Hence, the heat sink element 52 serves toselectively regulate the rate of temperature increase in element 40 formodulating the contact controlling action thereof.

One feature of the present invention is that the operative parts thereofcan be associated in an extremely compact manner. This is bestillustrated in FIGURES 3-8 where a structural embodiment of theinvention illustrated in FIGURE 2 is shown with like elements in theschematic view of FIGURE 2 and the structural views being designatedwith the same reference numerals. In the structural arrangement, thecontrol mechanism is enclosed in a housing 60 having a front cover 62with an opening wherein for receiving the shaft 32 which has one endthereof supported by the rear wall of the housing 60 at 64 for rotationrelative thereto. A snap ring 65 is secured to the shaft 32 at the endthereof to prevent axial movement thereof relative to housing 60. Thecam 26 is secured on the shaft 32 between the rear wall of the housing60 and the front cover '62 thereof for rotation relative thereto by theknob 34 which is secured to the end of the shaft 32 outwardly of thecover 62 for movement relative to the indicator 37 mounted on the outerface of the cover 62. The fixed contact 21 of the on-otf switch issecured by means of a suitable fastener to a rib 66 located at one sideof the housing 60- where a terminal 67 electrically connected thereto isadapted to be connected to a suitable source of power such as line 20 inFIGURE 2. The spring arm 24 is secured to the same side wall of thehousing 60 by means of a rivet 68 which also secures a terminal 70 inelectrical contact with the arm 24 with the terminal 70 being adapted tobe connected to a conductor such as 38 in FIGURE 2 leading to a surfaceheater unit such as 12.

The thermally responsive element 40 is secured at one end thereof on theopposite side of the cam 26 by a clip 72 secured to the housing 60adjacent the base thereof and is directed generally vertically of thehousing 60 upwardly from the clip 72 where a beveled upper end portion73 thereof contacts the cantilevered spring arm 44 adjacent one endthereof anchored to the housing 60 by means of a clip 74 secured theretoat 75.

In certain structural embodiments of the invention the physicaldimensions of element 40 reduce the electrical resistance thereof to apoint where it will not self-heat sufficiently to produce the transitiontemperature necessary for opening contacts 46, 48. In such cases anelectrical heater 76 is wound in heat transfer relationship with theelement 40 leaving one end thereof connected to a terminal 77 adapted tobe electrically connected to a conductor such as 39 in circuit with thedevice to be controlled. The opposite end of heater 76 is connected tothe spring arm 44 at 7-5 to complete an energizing circuit for theheater 76 when contacts 46, 48 are closed.

One feature of the structural arrangement is that when the knob 34 is inan off position, as shown, the cam 26 is positioned so that aprotuberance 79 on the upper portion thereof will contact an offset camfollower 80 secured to the underside of the spring arm 44 to positionthe contacts 46, 48 in an open position so that there will be notendency for pressure welding these controlling contacts when thecontroller is turned off. When the cam 26 is moved from its off positionthe protuberance 79 will move away from the follower 80 to allow thespring arm 44 to bias the contact 46 into engagement with the contact48. When the cam 26 is moved in this manner, it will also force thespring arm 24 in a direction to cause the contacts 21, 22 of the on-otfswitch to close to produce the above-discussed self-heating of theelement 40 and the consequent pulsating control of the contacts 46, 48to regulate the energization of an electrical device associated with thecontroller.

It should be noted that in structural arrangement of FIGURES 3-8 thelength of the spring arm 44 between the point at which the beveled end73 of the element 40 is in contact therewith and the contact carryingend thereof is substantially equal to the full width of the controllerhousing 60. This substantial length of the arm 44 in accordance withcertain of the principles of the present invention, produces anamplification of the expansion movement of element 40 at the transitiontemperature thereof suflicient to produce a desired spacing of thecontacts 46, 48 when they are in an open position to prevent arcingtherebetween.

It should be further noted that the contact 48 is secured to a screwelement 82 threadably engaged in a C-shaped internally threaded base 84to allow adjustment of the contact 48 relative to the contact 46 byinsertion of a suitable tool through an opening 85 in the housing 60 toprovide a predetermined adjustment of the spacing between the contacts46, 48 to calibrate the controller. The base 84 is secured to housing 60by a rivet 86 which also supports a terminal 87 in electrical contactthrough base 84 and screw 82 with contact 48. The terminal 87 is adaptedto connect to another line of a power source such as line 18 in FIGURE2.

Another feature of the illustrated structural embodiment of theinvention of FIGURE 2 is the manner in which the channel-shaped heatsink element 52 is supported for adjustment relative to the thermalresponsive element 40. It will be noted that in the structuralembodiment the spring 54 is illustrated as a flat spring having the endsthereof in engagement with the arm 58 of the heat sink 52 and a centralportion thereof secured to a rib 89 of the housing by means of a'clip 88so that the spring 54 will bias the heat sink element 52 against thecamming surface 56 on the cam 20 to provide for smooth sliding movementof heat sink element 52 relative to the element 40.

In the embodiment of the invention illustrated in FIG- URE 9 a suitablesource of power is connected to lines 100, 102 for energizing a surfaceheater 104 under the control of a thermally responsive element 106 likethe element 40 in the embodiment of FIGURE 2. In this arrangement acontrol knob 108 having a suitable scale 110 thereon is manuallyrotatable relative to an indicator 112 for rotating a shaft 114 to movea cam 116 relative to a cantilevered spring arm 118 of conductivematerial that is biased against the outer periphery of cam 116 and fixedat one end thereof to a fixed support 119. This causes an offset of arm118 to be moved from a notch 122 in the outer periphery of the cam 116so as to move a contact l24 secu'red to the end of the spring arm 118 inelectrical contact therewith into engagement with a fixed contact 126connected to line 102 to thereby close a circuit from the line 102through the contacts 124, 126, the arm 118, a conductor 128, the surfaceheater 104, a conductor 130, a cantilevered spring arm 132 of conductivematerial having one end thereof fixed at support 133 and having acontact 134 secured on the free end thereof spring biased intoengagement with a fired contact 136 electrically connected to the line100.

Concurrently with energization of the heater 104, current passes througha conductor 138 electrically connected to the conductor 128 and thencethrough an electrical heater element 148 in heat transfer contact withthe element 106 representatively illustrated as an insulated wire woundin heat transfer relationship therewith, and thence through a resistanceelement 150 of a potentiometer, its contact carrying rotatable arm 154,a conductor 156, conductor 130, the spring arm 132 of conductivematerial and line 100. The heater 148 serves to increase the temperatureof the thermally responsive element 106 until it reaches the transitiontemperature thereof to cause an expansion therein sufiicient to open thecontacts 134, 136 to thereby de-energize the heater 104.

In this embodiment of the invention the controlling action of theelement 106 is modulated by rotating the potentiometer arm 154 throughthe control knob 108. More particularly, the contact carrying arm 154 ofthe potentiometer is operatively associated with the shaft 114 connectedto the knob 108 so that when the knob 108 is rotated to a preselectedtemperature the contact carrying arm 154 is moved relative to theresistance element 150 to include a greater or lesser portion thereof incircuit with the heater 148 for varying the current flow therethrough tothereby vary the manner in which the element 106 is heated.

When it is desired to regulate the hater 104 to produce a relativelyhigh heat output therefrom, the knob 108 is rotated in a direction tocause a greater portion of the resistance 150 to be serially connectedin circuit with the heater 148. This reduces the current flow throughthe heater 148 to reduce the heat output therefrom so that it will takea longer period for the element 106 to reach the transition temperatureat which it will expand to open the contacts 134, 136. Accordingly, theelement 106 will heat and cool to produce a greater percentage ofenergization of the heater 104. When the knob 108 is rotated in adirection to include less of the resistance 150 in circuit with theheater 148, a greater current will flow therethrough to produce a morerapid heating of the element 106 to thereby cause it to reach itstransition temperature quicker. Thus, the percentage of energization ofthe heater 104 is reduced along with the heat output therefrom. Thepotentiometer thereby serves as a customer control since it willdetermine the length of time that power is supplied to the heater 104and also the length of time that power is removed from the heater 104.In other Words, it will provide a means for controlling the averagepower input to the surface unit 104.

While the embodiments of the present invention as herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An electrical control device associable with a power source forregulating the energization of an electrical device comprising, meansincluding a pair of contacts for interrupting current flow from thepower source to the controlled device, a thermally responsive elementhaving a predetermined transition temperature at which it abruptlyexpands, means for heating said thermally responsive element to saidpredetermined transition temperature, means for connecting saidthermally responsive element to one of said pair of contacts for movingsaid contacts to an open position when said thermally responsive elementreaches said predetermined transition temperature for controlling theenergization of the controlled device, an element of thermal conductivematerial serving as a heat sink, means for supporting said element ofthermal conductive material in heat transfer relationship with saidthermally responsive element, and means varying the heat transferrelationship between said thermal conductive element and said thermallyresponsive element to vary the heat sink capacity of said thermalconductive element for varying the rate of temperature increase of saidthermally responsive element to modulate the contact controlling actionthereof.

2. An electrical controller comprising a housing, a temperatureresponsive element having a predetermined transition temperature atwhich it abruptly expands, said thermally responsive element having oneend portion fixed to said housing and another end portion free to expandrelative thereto, means for heating said thermally responsive element tosaid predetermined transition temperature, a fixed contact, a movablecontact, a cantilevered spring arm of conductive material secured tosaid movable contact for biasing it into engagement with said fixedcontact, said cantilevered spring arm extending across the width of saidhousing, means for electrically connecting said cantilevered spring armand said fixed contact in circuit with an electrical device energized bya power source controlled by said fixed and movable contacts, anotherend of said thermally responsive element engaging said cantileveredspring arm adjacent the anchored end thereof a substantial distance fromthe contact carrying end thereof, said thermally responsive element uponsensing a predetermined temperature abruptly expanding to move saidcantilevered spring arm for separating said movable contact from saidfixed contact to control the energization of the electrical device anelement of thermal conductive material having portions thereofoverlapping said thermally responsive element in heat transferrelationship therewith to serve as a heat sink, a cam element engagingsaid heat conductive element, means for resiliently biasing said thermalconductive element against said cam, means for rotating said camrelative to said thermal conductive element for causing movement thereofrelative to said thermally responsive element to vary the heat sinkcapacity of said thermal conductive element for regulating the rate oftemperature increase of said thermally responsive element to therebymodulate the contact controlling action thereof.

3. A controller comprising a housing, a temperature responsive elementhaving a predetermined transition temperature at which it abruptlyexpands, said thermally responsive element having one end portion fixedto said housing and another end portion free to expand relative thereto,means for heating said thermally responsive element to saidpredetermined transition temperature including an electrical heaterlocated in heat transfer relationship with said thermally responsiveelement, a fixed contact, a movable contact, a cantilevered spring armof conductive material secured to said movable contact for biasing itinto engagement with said fixed contact, said cantilevered spring armextending across the width of said housing, means for electricallyconnecting said cantilevered spring arm and said fixed contact incircuit with an electrical device energized by a power source controlledby said fixed and movable contacts, said another end of said thermallyresponsive element engaging said cantilevered spring arm adjacent theanchored end thereof a substantial distance from the contact carryingend thereof, said thermally responsive element upon sensing apredetermined temperature abruptly expanding to directly move saidcantilevered spring arm for separating said movable contact from saidfixed contact to control the energization of the electrical device whensaid thermally responsive element reaches said predetermined transitiontemperature with the expansion of said thermally responsive elementbeing amplified through the cantilevered spring arm for maintaining adesired separation 7 between said fixed and movable contacts when theyare in their opened position, and means for varying the heat out put ofsaid heater for regulating the rate of temperature increase of saidthermally responsive element to thereby modulate the contact controllingaction thereof.

References Cited by the Examiner UNITED STATES PATENTS 8 3,078,3612/1963 Mason et al. 200-122 3,254,180 5/1966 Flanagan 200-113 FOREIGNPATENTS 461,166 10/1913 France.

OTHER REFERENCES Hansen, Max: Constitution of Binary Alloys, New York,McGraw-Hill, Inc., 1958.

1,642,485 10/ 1927 Chace.

2,162,343 6/ 1939 Brace 200-122 X 10 BERNARD A. GILHEANY, PrimaryExaminer. 2,315,565 4/1943 Waltenberm 2,814,694 11/1957 Moodie f 200-137H. A. LEWITTER, L. A. WRIGHT, Asszstant Examiners.

1. AN ELECTRICAL CONTROL DEVICE ASSOCIABLE WITH A POWER SOURCE FORREGULATING THE ENERGIZATION OF AN ELECTRICAL DEVICE COMPRISING, MEANSINCLUDING A PAIR OF CONTACTS FOR INTERRUPTING CURRENT FLOW FROM THEPOWER SOURCE TO THE CONTROLLED DEVICE, A THERMALLY RESPONSIVE ELEMENTHAVING A PREDETERMINED TRANSITION TEMPERATURE AT WHICH IT ABRUPTLYEXPANDS, MEANS FOR HEATING SAID THERMALLY RESPONSIVE ELEMENT TO SAIDPREDETERMINED TRANSITION TEMPERATURE, MEANS FOR CONNECTING SAIDTHERMALLY RESPONSIVE ELEMENT TO ONE OF SAID PAIR OF CONTACTS FOR MOVINGSAID CONTACTS TO AN OPEN POSITION WHEN SAID THERMALLY RESPONSIVE ELEMENTREACHES SAID PREDETERMINED TRANSITION TEMPERATURE FOR CONTROLLING THEENERGIZATION OF THE CONTROLLED DEVICE, AN ELEMENT OF THERMAL CONDUCTIVEMATERIAL SERVING AS A HEAT SINK, MEANS FOR SUPPORTING SAID ELEMENT OFTHERMAL CONDUCTIVE MATERIAL IN HEAT TRANSFER RELATIONSHIP WITH SAIDTHERMALLY RESPONSIVE ELEMENT, AND MEANS VARYING THE HEAT TRANSFERRELATIONSHIP BETWEEN SAID THERMAL CONDUCTIVE ELEMENT AND SAID THERMALLYRESPONSIVE ELEMENT TO VARY THE HEAT SINK CAPACITY OF SAID THERMALCONDUCTIVE ELEMENT FOR VARYING THE RATE OF TEMPERATURE INCREASE OF SAIDTHERMALLY RESPONSIVE ELEMENT TO MODULATE THE CONTACT CONTROLLING ACTIONTHEREOF.